Additive for tin electroplating

ABSTRACT

THE PRESENT INVENTION PROVIDES A TIN-PLATING ADDITIVE COMPRISING A PROPORTION WITHIN THE RANGE OF FROM 0.0125% TO 98.7% BY WEIGHT BASED ON THE TOTAL WEIGHT OF THE ADDITIVE OF 4:4&#39;&#39;-DI (DIMETHYLAMINO) DIPHENYLMETHANE AND ONE OR MORE TIN-PLATING ADDITIVES FUNCTIONALLY ACTIVE IN AN ACIDIC TIN-PLATING BATH.

U.S. Cl. 204-54 United States Patent O 3,691,033 ADDITIVE FOR TINELECTROPLATIN Donald Kearey Howard, Levenshulme, Manchester, Brian land,and Dario Matossi, Pamplona, Spain, assignors to Ciba-Geigy CorporationNo Drawing. Filed Feb. 24, 1970, Ser. No. 13,766 Int. Cl. C23b 5/14, 5/46 R 5 Claims ABSTRACT OF THE DISCLOSURE I The present inventionprovides a tin-plating additive of the additive of 4:4'-di[dimethylamino] diphenylmethane and one or more tin-plating additivesfunctionlally active in an acidic tin-plating bath.

The present invention relates to new tin-plating additives and totin-plating baths containing the additives.

'It is known to use acidic tin-plating baths containing tin in thestannous form together with small amounts of organic additives. Theincorporation of such organic additives into the tin-plating bath ismade in order to increase the range of current density over whichacceptable plating may be achieved. Examples of known organic tinplatingadditives include condensed sulphonated phenol mixtures described andclaimed in British patent specification No. 1,033,662.

However, by means of the incorporation of a tin-plating additive knownfor use in acidic baths or a mixture of such additives at their knownworking concentrations, acceptable plating is still only obtained withincertain approximate limits of current density, for instance from about60 amperes/square foot to about'450 amperes/ square foot. Even at veryhigh levels of addition, acceptable plating cannot be obtained at highcurrent densities using known tin-plating additives alone or inadmixture. In the specific case of 4:4 [dimethylamino] diphenylmethane,it is possible by the addition of very large amounts of this additive toachieve acceptable plating at very low current density but only at theexpense of exceeding its solubility level in the bath and by recourse tothe use of high voltages.

We have now discovered that a mixture of 4:4'-di [dimethylamino]diphenylmethane and one or more other tin-platingadditives known to befunctionally active in acidic tin-plating baths, when added at a similarlevel of concentration as conventional additives to an acidic tinplatingbath produces surprising synergistic effects resulting in satisfactoryplating over a considerably wider range of current densities than can beobtained by the use of any of the additives singly or in otheradmixture.

Accordingly, the present invention provides a tin-plating additivecomprising a proportion within the range of from 0.0125% to 98.7% byweight based on the total weight of the additive of 4:4-di[dimethylamino] diphenylmethane and one or more tin-plating additivesfunctionally active in an acidic tin-plating bath.

The present invention also provides a process in which a tin-platingadditive is produced comprising admixing a proportion with the range offrom 0.0125 to 98.7% by weight of 4:4'-di [dimethylamino]diphenylmethane and one or more tin-plating additives functionallyactive in acidic tin-plating baths.

Although the 4:4'-di [dimethylamino] diphenylmethane may be employedsuccessfully in high proportions ice in the tin-plating additive of thepresent invention, for optimal technical and economic advantage it ispreferred not to exceed a proportion of 10% by Weight. Thus, if morethan 10% by Weight of 4:4'-di [dimethylamino] diphenylmethane is presentin the total additive, unacceptable levels of sludge-formation and/or ofbath discolouration are observed in the tin-plating bath into which thetin-plating additive of the present invention is incorporated. Apreferred range of proportions of 4:4'-di [dimethyl amino]diphenylmethane in the total tin-plating additive is therefore from0.0125 to 10% by weight, from 0.1% to 2.0% by weight being particularlypreferred.

' The second component of the tin-plating additive of the presentinvention may be selected from a range of additives known to befunctionally active in increasing the range of current density overwhich acceptable plating can be achieved in conventional acidictin-plating bath,

especially the so-called Ferrostan bath, comprising an aqueous solutionof stannous tin and phenol sulphonic acid. As examples of suitableadditives there may be mentioned the sulphonated phenol additivesproduced according to the process described and claimed in Britishpatent specification No. 1,033,662 that is a process comprisingsulphonating phenol and/or cresol with oleum containing from 60% to 66%by weight of sulphur trioxide and thereafter heating the resultingsulphonated product for at least one hour without adding further phenol,at a subatmospheric pressure of from 5 to 25 millimeters of mercurypressure, and at a temperature in the range of from to C.; thephenol/polyol condensation products described in claimed in Britishpatent specification No. 1,221,688, that is produced by reacting phenoland an aliphatic polyol containing from 2 to 8 hydroxy groups permolecule in 1:1 to 10:1 molar proportions respectively, the condensationreaction being carried out at a temperature of from 50 C. to 250 C. fora period of 1 to 10 hours; sulphonated Bisphenol A(2:2'-di-pphenylolpropane) in acetic acid solution described and claimedin British Pat. No. 1,146,588; and an additive consisting essentially ofdihydroxydiphenyl sulphone and sold under the trademark Phenolene.

Preferably the proportion of the second tin-plating additive is withinthe range of from 90% to 99.9875% by weight, more preferably within therange of from 98% to tin available for electro-plating a source ofhydrogen ions and an additive comprising a proportion within the rangeof from 0.012% to 98.7% by weight of 4:4-di [dimethylamino]diphenylmethane and from 99.987% to 1.3% by weight of one or morefunctionally-active tin-plating additives.

It is preferred to use stannous sulphate as the source of tin ions. Theproportion of tin salt in the tin-plating bath is advantageously withinthe range of from 1.0% to 20% by weight, more preferably Within therange of from 2.0% to 10% by weight, based on the total weight of thetinplating bath.

The proportion of the tin-plating additive of the present invention inthe tin-plating bath may be, for example, within the range of from 0.01%to 10% by weight, and preferably within the range of from 0.01% to 5% byweight, based on the total weight of the tin-plating bath.

In addition to the source of tin ions and the tin-plating additive ofthe present invention, the tin-plating bath desirably contains as thesource of hydrogen ions, phenol sulphonic acid, the source of hydrogenions preferably being present in a proportion within the range of from0.1% to 20.0% by weight, more preferably Within the range of from 0.5%to 10.0% by weight based on the total weight of the tin-plating bath.

The tin-plating additive of the present invention provides acceptabletin-plating from acidic tin-plating baths over a very wide range ofcurrent density. Moreover, the tin-plating additive of the presentinvention is compatible with other tin-plating bath components in allproportions which are conventionally employed for additives in acidictin-plating baths.

The present invention is further illustrated by the folrelating to theplating results achieved When, as the tinplating additive, a mixture ofequal parts by weight of additives (a) and (b) listed above is employedin the standard Hull test.

As a still further comparative aid, data is presented in the tablerelating to the plating results achieved when only 4:4-di[dimethylamino] diphenylmethane is employed as the tin-plating additivein the standard Hull test.

TAB LE Range of current density over which acceptable plating isachieved (amps/square loot) Band Band Actual Hull position width Cellcurrent Current Example Additives present in bath (grams/litre) (cm.)(cm.) densities densities l Phouolene supra (condensation product ofsulphonated o-cresol) (4.0) 3. 3 6. 5 68-1. 5 450-64 Diplionc V(sulphonated Bisphenol A derivative) (4.0) 4.6 4.6 45-20 299-86Dihydroxydiphenylsulphone (6.0) 4.3 5.5 481.5 330-64 Phenol/glucosecondensation product (4.0) 4. 7 5.1 45-1. 5 289-64 Diphone V (2.0) plusphenolene supra (2.0) 4. 3 5. 5 48-1. 5 330-64 Phcnolene supra (4.0)plus dihydroxydiphenyl sulphone (1.0) 4. 1 5. 5 55-1. 5 350-72 'IMADM(0.02) 5. 5 0.0 N N11 TMADM (2.0) 4. 2. 0 50-30 350-260 Phenoleue supra(4.0) plus TMADM (0.02) 0. 2 9. 120-l. 5 700-68 2. Diphone V (4.0) plusTMADM (0.04) 0.4 9.1 1201.5 700-76 3. Dihydroxydiphenyl sulphone (6.0)plus TMADM (0.06) 0.3 9. 7 l-1. 2 700-55 4... Phenol/glucosecondensation product (2.0) plus TMADM (0.02) 0. 6 9. 0 120-1.5 700-76 5Phenolene supra (4.0) plus dihydroxydiphenyl sulphone (1.0) plus T AD(0.04).. 0.4 9.1 120-1. 7 700-76 As corrected to allow for commercialplating line conditions.

lowing examples. Parts and percentages shown therein are by weightunless otherwise stated. Parts by weight bear the same relation to partsby volume as do kilograms to litres.

EXAMPLES l to 4 The acidic tin-plating bath solution having thefollowing construction was made up.

55 parts by weight of an electroplating grade of stannous sulphate (toBritish Standard 1468:1948) parts by weight of phenol sulphonic acid 915parts by weight water To this solution was added 4:4'-di [dimethylamino]diphenylmethane in conjunction with the various tin-plating additivemixtures listed below in the respective amounts per litre as given inthe following table.

(a) the commercially-available product Phenolene Supra (Phenolene is aregistered trademark) which is a condensation product derived fromsulphonated 0- cresol produced as described in British patentspecification No. 1,033,662.

(b) the commercially-available product Diphone V which is believed to bea sulphonated Bisphenol A derivative and is also believed to bedescribed and claimed in British Pat. No. 1,146,588.

(c) the commercially-available product Phenolene which consistssubstantially of dihydroxydiphenyl sulphone. (Phenolene is a registeredtrademark).

(d) a phenol/ glucose condensation product described and claimed in ourBritish patent specification No. 1,221,688.

250 millilitres of each of the respective solutions were placed in turnin a standard 350 millilitres Hull cell (W. Nohse, the Hull Cellpublished by R. Draper Limited, 1966) and plating was carried out at 3.0amps at 50 C. for one minute. The results obtained are summarised in thetable.

For the purpose of comparison, data are also included in the tablerelating to the use of the additives listed under headings (a) to (d)alone, that is, in the absence of 4:4'- di [dimethylamino]diphenylmethane (TMADM) in Hull cell tests under the standard conditionsdescribed in the previous paragraph.

As a further comparative aid, data is given in the table What we claimis:

1. A tin electroplating additive comprising a proportion within therange of from 0.0125 to 98.7% by weight based on the total weight ofadditive of 4,4-di [dimethylamino] diphenylmethane and at least one tinplating additive selected from sulphonated phenol additives produced bysulphonating phenol and/or cresol with oleum containing from 60% to 66%by weight of sulphur trioxide and thereafter heating the resultingsulphonated product for at least one hour without adding further phenol,at a subatmospheric pressure of from 5 to 25 millimeters of mercury andat a temperature in the range of from C. to C.; the phenol/polyolcondensation products produced by reacting phenol and an aliphaticpolyol containing from 2 to 8 hydroxyl groups per molecule in a 1:1 to10:1 molar proportions respectively the condensation reaction beingcarried out at a temperature of from 50 C. to 250 C.; sulphonatedBisphenol A (2,2'-di-p-phenylolpropane) in acetic acid solution; and anadditive consisting essentially of dihydroxydiphenyl sulphone.

2. A tin electroplating additive as claimed in claim 1 wherein theproportion of 4:4'-di [dimethylamino] diphenylmethane in the totaltin-plating additive is within the range of from 0.0125% to 10% byweight.

3. A tin electroplating additive as claimed in claim 2 wherein theproportion of 4:4'- [dimethylamino] diphenylmethane in the totaltin-plating additive is within the range of from 0.1% to 2.0% by weight.

4. A tin electroplating additive as claimed in claim 1 wherein theproportion of the second component is within the range of from 90% to99.9875% by weight of the total additive.

5. A tin electroplating additive as claimed in claim 4 wherein theproportion of the second component is within the range of from 98% to99.9% by weight of the total additive.

References Cited UNITED STATES PATENTS 3,558,703 1/1971 Adam et a].260-576 X 2,633,450 3/ 1953 Andrews 20454 R 3,515,653 6/1970 Sykes 20454R GERALD L. KAPLAN, Primary Examiner U.S. Cl. X.R. 204DIG. 2

